1. Field of the Invention
The present invention relates to a numerical control method for compensating for a delay of a servo system in responding to a moving command so as to repetitively perform reciprocal movement of a controlled object at a high speed between target positions inclusive of these target positions.
2. Description of the Related Art
Conventionally, it has been known to drive a controlled object for repetitive reciprocal movement by means of a numerical control apparatus through a servo system. In numerical control of this kind, it has been also known to effect acceleration/deceleration control on a moving command supplied from the numerical control apparatus, i.e., a command pulse train (hereinafter referred to as command pulses), so as to reduce a response delay of the servo system, and to relieve load applied to the servo system, etc. upon inversion of the sign of the command pulses (upon start of and completion of delivery of the command pulses). However, in the case of acceleration/deceleration control being effected, a period of time for execution of reciprocal movement increases. On the other hand, in order to shorten the execution time, if the delivery of command pulses for forward or backward movement of the controlled object is immediately followed by the delivery of the subsequent command pulses for opposite movement, i.e., for backward or forward movement of the controlled object, without acceleration/deceleration control being performed, the subsequent command pulses, having the sign opposite that of the former command pulses, are delivered before the controlled object reaches the target position, so that the remaining part of the former command pulses is canceled by an initial part of the latter command pulses. As a result, the moving direction of the controlled object is reversed immediately before the target position is reached, and hence the controlled object cannot reach the target position. Accordingly, it is impossible to accurately carry out the reciprocal movement of the controlled object between the target positions inclusive of these positions, in accordance with the commanded locus.